More specifically, the invention relates to a flap device comprising: a support structure in which is formed a passage in which a tab-like shutter or flap is fitted pivotally about an operationally horizontal axis nearer to a first end of the shutter, between a lowered rest position in which it closes the passage and a raised operating position in which it opens the passage, thereby allowing a flow of air to pass in a predetermined direction through the passage. The arrangement being such that, in use, the shutter or flap pivots from the lowered rest position towards the raised operating position under the effect of a flow of air which strikes it in this direction, and returns by gravity towards the rest position when the air flow ceases. The shutter or flap having at least one support part intended to strike against associated stop surface of the support structure when the shutter or flap reaches the rest condition.
FIG. 1 of the attached drawings shows an electric fan unit 1 for a heat exchanger (a radiator) of a motor vehicle. This fan unit comprises a plate-like support structure or cowl 2, having a circular opening 3 in which an electric fan, indicated as a whole by 4, is fitted.
In a known way, the electric fan 4 comprises an electric motor, not visible in FIG. 1, the rotor of which is coupled to a rotary fan or impeller 5 comprising a central hub 6 from which there extends a plurality of curved blades 7, the distal ends of which are joined to a peripheral ring 8.
In the embodiment illustrated by way of example in FIG. 1, the support structure or cowl 2 has, at its corners, respective flap devices indicated collectively by 9, each including a respective essentially rectangular passage 10 which is associated with a tab-like shutter or flap 11 of essentially rectangular shape.
In each flap device 9, the tab-like shutter or flap 11 is pivotable about an operationally horizontal axis X-X, between a lowered rest condition, shown in FIGS. 1 and 3, in which it closes the associated passage 10, and a raised operating position (shown partially in broken lines in FIG. 3) in which it opens the associated passage 10, thereby allowing a flow of air to pass in a predetermined, essentially horizontal, direction through the passage. The pivot axis X-X of each shutter or flap 11 is nearer a first end 11a thereof.
The arrangement is such that, in use, the shutter or flap 11 pivots from the lowered rest position towards a raised operating position under the effect of a flow of air which strikes it in the aforesaid predetermined direction, and returns by gravity towards the rest position when this air flow ceases.
In the prior art solution, to which FIGS. 2 and 3 of the attached drawings refer, the other or second end 11b of the shutter or flap 11, farther from the axis X-X, has a stop element indicated by 11c in FIG. 3, intended to strike against an associated abutment surface 2a of the support structure or cowl 2 when the shutter or flap 11 reaches the rest condition.
The first end 11a of the shutter or flap 11 has an edge 12 (FIGS. 2 and 3) which, in the rest condition, faces and is spaced apart from a portion 2b of the supporting structure or cowl 2 (FIG. 3) which forms one side of the opening or passage 10.
In use, the shutters or flaps 11 of the devices 9 of FIG. 1 tend to move from the rest position to the open operating position under the action of air flows which strike them as a result of the forward movement of the motor vehicle. When these flows cease, in other words when the motor vehicle slows down and stops, these shutters or flaps return to the closed rest position under the effect of gravity.
With the known solution described above, the shutters or flaps generate an annoying closing noise, for example when the engine is switched off and the driver and any passengers leave the motor vehicle and close its doors.
This problem affects not only motor vehicles having conventional thermal engines, but also motor vehicles having purely electric or hybrid traction systems requiring cooling fans for radiators, battery packs, etc. Such flap devices may be used with fan units have fans driven by the engine of the vehicle.